Structures and Energetics of Cu21-Cu71 Clusters: A Molecular Dynamics Study (original) (raw)
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Zeitschrift f�r Physik D Atoms, Molecules and Clusters, 1997
Cluster properties of copper have been investigated using the Molecular-Dynamics md technique. The structural stability and energetics of spherical Cu n (n = 13 − 135) clusters have been investigated at temperatures T = 1 K and T = 300 K. It has been found that the average interaction energy per atom in the cluster decreases and reaches an asymptotic value as cluster size increases. The melting behaviour of clusters n = 13 and n = 55 have been investigated. It has been found that the melting temperature decreases as cluster size increases, and for clusters with multishell structures melting starts from the outermost shell. In the simulation an emprical potential energy function (PEF) proposed by Erkoç has been used, which contains two-body atomic interactions.
Structures and melting of Cun (n=13, 14, 19, 55, 56) clusters
Surface Science, 2003
Constant-energy molecular dynamics simulation was utilized to study the most stable geometrical structures, binding energy, melting, phase changes of Cu n (n ¼ 13, 14, 19, 55, 56) clusters. These sizes form shell and near shell structures. The cohesion of clusters is modeled by an embedded-atom potential, which contains many-body atomic interaction terms. Phase space coordinates which are generated along high-energy trajectories are used as the initial configurations (500 independent configurations) for thermal quenching in order to obtain the most stable isomers. The melting temperatures of the clusters are estimated. The melting-like transition is described in terms of relative root-mean-square bond-length fluctuations, specific heats, and caloric curves.
Structure and energetics of CuN clusters with (2⩽N⩽150): An embedded-atom-method study
Physical Review B, 2006
We use the embedded-atom method ͑EAM͒ in the version of Daw, Baskes, and Foiles ͑DBF͒ to determine the three most stable isomers of Cu N clusters with N from 2 to 150. Randomly generated initial configurations are optimized with the variable metric/quasi-Newton method combined with our own Aufbau/Abbau algorithm for searching the global minima. A detailed comparison is made for clusters with up to 60 atoms obtained with the DBF and the Voter-Chen ͑VC͒ versions of the EAM, the many-body Gupta, and the Sutton-Chen 9-6 potentials. Although the two EAM potentials have completely different parametrizations, they yield clusters that are structurally and energetically almost identical. On the other hand, the Sutton-Chen potential strongly overestimates the binding energy of the dimer and the small copper clusters with up to 15 atoms, and therefore, yields clusters with shorter bond lengths. For DBF clusters with up to 150 atoms we analyze many structural and energetic properties such as the overall shape, the construction of atomic shells, the similarity of the clusters with fragments of the fcc crystal or of a large icosahedral cluster, and whether the N-atom cluster resembles the ͑N −1͒-atom one with an extra atom added. The most stable clusters have high symmetry, such as the magic-sized Cu 55 and Cu 147 that are the second and third Mackay icosahedra, where the latter was obtained for the first time in a completely unbiased structure optimization. The cluster growth is predominantly icosahedral, with islands of fcc, tetrahedral, and decahedral growth.
Structural and energetic analysis of copper clusters: MD study of Cu n (n = 2-45)
Journal of the Brazilian Chemical Society, 2008
Simulações usando a dinâmica molecular foram efetuadas, considerando-se um potencial empírico para investigar geometrias, padrões de crescimentos, estabilidades de estruturas e energias para clusters de Cu n (n = 2-45). Os clusters estáveis otimizados foram calculados pelo rearranjo via processo de colisão. O presente procedimento apresenta-se como uma alternativa eficiente para a identificação do crescimento de clusters e como uma técnica de otimização. Foi verificado que os clusters de cobre preferem formar estruturas compactas tridimensionais em determinadas configurações enquanto os sistemas de tamanho médio apresentam simetria esférica. Além disso, também foram observadas correlações entre os arranjos atômicos e os números mágicos dos clusters. Particularmente, verificou-se que Cu 26 tem uma estabilidade equivalente ao sistema Cu 13. Molecular dynamics simulations, via an empirical potential, have been performed in order to investigate geometries, growing patterns, structural stabilities, energetics, and magic sizes of copper clusters, Cu n (n = 2-45). Possible optimal stable structures of the clusters have been generated through following rearrangement collision of the system in fusion regime. This process serves as an efficient alternative to the growing path identification and the optimization techniques. It has been found that copper clusters prefer to form three-dimensional compact structures in the determined configurations and the appearances of medium sizes are five fold symmetry on the spherical clusters. Moreover, relevant relations between atomic arrangements in the clusters and the magic sizes have been observed. Cu 26 may be accepted as another putative magic size like Cu 13 .
Structures and stability of the Cu$_{38}$ cluster at finite temperature
2022
The UV-visible and IR properties of the Cu38 nanocluster depend to a great extent on the temperature. Density functional theory and nanothermodynamics can be combined to compute the geometrical optimization of isomers and their spectroscopic properties in an approximate manner. In this article, we investigate entropy-driven isomer distributions of Cu38 clusters and the effect of temperature on their UV-visible and IR spectra. An extensive, systematic global search is performed on the potential and free energy surfaces of Cu38 using a two-stage strategy to identify the lowest-energy structure and its low-energy neighbors. The effects of temperature on the UV and IR spectra are considered via Boltzmann probability. The computed UV-visible and IR spectrum of each isomer is multiplied by its corresponding Boltzmann weight at finite temperature. Then, they are summed together to produce a final temperature-dependent, Boltzmann-weighted UV-visible and IR spectrum. Additionally, Molecular Dynamics simulation of the Cu38 nanocluster was performed to gain insight into the system dynamics and make a three-dimensional movie of the system with atomistic resolution. Our results show the thermal populations at the absolute temperature of Cu38 cluster, and the disordered structure that dominates at high temperatures.
Study of the Geometric Structure of Low-Atomic Copper Clusters Using Computer Simulation
2021
In this work, we investigated the geometric structure of small neutral copper clusters with low energy using the MD (Molecular Dynamics) method. When calculating the processes of interatomic interaction, we used a potential EAM (Embedded-atom method). A computer model of Cun (n = 2-13) clusters has been created. The geometric shapes of the Cu2, Cu3, Cu4, Cu5, Cu6, Cu7, Cu8, Cu9, Cu10, Cu11, Cu12, and Cu13 clusters have been studied and the structural parameters (Cu-Cu bond distance) have been calculated. The results obtained in the computer model were compared with the experimental results
Molecular dynamics study of the binding energy, sructure and melting of the isomers of Ni 8 clusters
Ari - An International Journal for Physical and Engineering Sciences, 1998
Using constant-energy molecular dynamics simulations, we have studied minimum-energy geometries, binding energies and melting behaviour of Ni8 clusters employing embedded-atom potential energy surface. The melting-like transition is described in terms of relative root-mean-square bond-length fluctuations. We have obtained four isomers of Ni8, three of which are stable. Melting temperature of the Ni8 cluster is about 600 K.
Structure and energetics of nickel, copper, and gold clusters
The European Physical Journal D, 2005
The most stable structures of CuN , NiN , and AuN clusters with 2 ≤ N ≤ 60 have been determined using a combination of the embedded-atom (EAM), the quasi-Newton, and our own Aufbau/Abbau methods for the calculation of the total energy for a given structure, the structures of the local total-energy minima, and the structure of the global total-energy minimum, respectively. We have employed two well-known versions of the EAM: (1) the 'bulk' version of Daw, Baskes, and Foiles and the Voter-Chen version which takes into account also properties of the dimer in the parameterization. The lower-energy structures (also for the smallest) of CuN and NiN clusters (i.e., structural details as well as symmetry) obtained with the two versions are very similar. Thus, our study supports an universality of the bulk embedding functions for copper and nickel. But for gold clusters the differences between structures calculated with the two different versions of the EAM are significant, even for larger clusters.
Frontiers in Chemistry, 2022
The relative populations of Cu38 isomers depend to a great extent on the temperature. Density functional theory and nanothermodynamics can be combined to compute the geometrical optimization of isomers and their spectroscopic properties in an approximate manner. In this article, we investigate entropy-driven isomer distributions of Cu38 clusters and the effect of temperature on their IR spectra. An extensive, systematic global search is performed on the potential and free energy surfaces of Cu38 using a two-stage strategy to identify the lowest-energy structure and its low-energy neighbors. The effects of temperature on the populations and IR spectra are considered via Boltzmann factors. The computed IR spectrum of each isomer is multiplied by its corresponding Boltzmann weight at finite temperature. Then, they are summed together to produce a final temperature-dependent, Boltzmann-weighted spectrum. Our results show that the disordered structure dominates at high temperatures and t...
First principles studies on the growth of small Cu clusters and the dissociative chemisorption of H2
Physical Review B, 2006
The sequential growth of small copper clusters up to 15 atoms and the dissociative chemisorption of H 2 on the minimum energy clusters are studied systematically using density functional theory under the generalized gradient approximation. We found that small Cu n clusters grow by adopting a triangular growth pathway. The pentagon bipyramid structural arrangements are strongly favored energetically in the growth and the new addition in the cluster occurs preferably at a site where the atom is capable of interacting with more adjacent atoms. To understand the evolution of small copper clusters, we also performed calculations on selected icosahedral clusters ͑for n = 13, 19, 25, 55͒ and fcc-like clusters ͑n = 14, 23, 32, 41͒. By extrapolating/ interpolating the binding energies of triangular clusters, icosahedral clusters, and bulk-like clusters, we found that structural transitions from the triangular growth clusters to the icosahedral and fcc-like clusters occur at approximately n = 16 and n = 32, respectively. Subsequently, we performed extensive calculations on the dissociative chemisorption of H 2 on the minimum energy clusters. The chemisorption likely occurs near the most acute metal site with the two H atoms residing on the edges, which differs significantly from the chemisorption on Cu surfaces that usually takes place at the hollow sites.